The radio frame in the long term evolution (LTE) system includes frame structures of frequency division duplex (FDD) mode and time division duplex (TDD) mode. The frame structure of FDD mode is as shown in FIG. 1, wherein one 10 ms radio frame is composed of twenty slots with the length thereof being 0.5 ms and numbered as 0-19, and slots 2i and 2i+1 form a subframe i with the length thereof being 1 ms. The frame structure of TDD mode is as shown in FIG. 2, wherein one 10 ms radio frame is composed of two half frames with the length thereof being 5 ms, one half frame includes 5 subframes with the length thereof being 1 ms, and subframe i is defined as 2 slots 2i and 2i+1 with the length thereof being 0.5 ms. In the above two frame structures, as to normal cyclic prefix (Normal CP), one slot includes 7 symbols with the length thereof being 66.7 us, wherein the CP length of the first symbol is 5.21 us, and the CP length of the remaining 6 symbols is 4.69 us; and as to an extended cyclic prefix (Extended CP), one slot includes 6 symbols, and the CP length of all the symbols is 16.67 us.
The release number of LTE corresponds to Release 8 (R8), and added release corresponds to the release number of Release 9 (R9), and as to the subsequent LTE-Advance, its release number is Release 10 (R10). The following three physical downlink control channel are defined in LTE: Physical Control Format Indicator Channel (PCFICH), Physical Hybrid Automatic Retransmission Request Indicator Channel (PHICH), and Physical Downlink Control Channel (PDCCH).
In this case, the information carried by PCFICH is used for indicating the number of orthogonal frequency division multiplexing (OFDM) symbols of the PDCCH transmitted in one subframe and it is sent on the first OFDM symbol of the subframe, and the frequency location thereof is determined by the system downlink bandwidth and the cell identity (ID).
PHICH is used for carrying Acknowledge/Non-acknowledge (ACK/NACK) feedback information of the uplink transmission data. The number and time frequency location of PHICH can be determined by the system message and cell ID in a physical broadcast channel (PBCH) of a downlink carrier where PHICH is located.
PDCCH is used for carrying downlink control information (DCI), including uplink/downlink scheduling information and uplink power control information. The formats of DCI are classified as: DCI format 0, DCI format 1, DCI format 1A, DCI format 1B, DCI format 1C, DCI format 1D, DCI format 2, DCI format 2A, DCI format 3, DCI format 3A and so on, wherein
DCI format 0 is used for indicating the scheduling of the physical uplink shared channel (PUSCH);
DCI format 1, DCI format 1A, DCI format 1B, DCI format 1C, DCI format 1D are used for different modes of scheduling one PDSCH codeword;
DCI format 2, DCI format 2A, and DCI format 2B are used for different modes of space division multiplexing;
DCI format 3 and DCI format 3A are used for different modes of power control instructions of physical uplink control channel (PUCCH) and PUSCH.
In this case, the sizes of DCI format 3 and 3A are consistent with that of DCI format 0. In this case, in DCI format 3, two continuous bits are used for indicating the transmit power control (TPC) commands of PUCCH and PUSCH, a high layer signaling (tpc-Index) designates the starting position of the TPC command of a certain user, while in DCI format 3A, 1 bit is used for indicating the transmit power control (TPC) commands of PUCCH and PUSCH, and a high layer signaling (tpc-Index) designates the starting position of the TPC command of a certain user.
In pariticular, DCI format 3 employs 2 bits to transmit the TPC command for PUCCH and PUSCH, and the following information is indicated by DCI format 3:
TPC command 1, TPC command 2, . . . , TPC command N
In this case,
      N    =          ⌊                        L                      format            ⁢                                                  ⁢            0                          2            ⌋        ,Lformat 0 is equal to the size before DCI format 0 adds cyclical redundancy check (CRC), including any added bits, and └ ┘ represents round down. And, the parameter tpc-Index provided by the high layer signaling is used for designating the index of the TPC command for a certain user.
If
            ⌊                        L                      format            ⁢                                                  ⁢            0                          2            ⌋        <                  L                  format          ⁢                                          ⁢          0                    2        ,then one 0 bit will be added into DCI format 3.
In pariticular, DCI format 3A employs 1 bit to transmit the TPC command for PUCCH and PUSCH, and the following information is indicated by DCI format 3A:
TPC command 1, TPC command 2, . . . , TPC command M
In this case, M=Lformat 0, Lformat 0 is equal to the size before DCI format 0 adds CRC, including any added bits. And, the parameter tpc-Index provided by the high layer signaling is used for designating the index of the TPC command for a certain user.
The physical resources transmitted by the physical downlink control channel (PDCCH) are in the unit of control channel element (CCE), and the size of one CCE is 9 resource element groups (REG), i.e. 36 resource elements (RE), and one PDCCH may occupy 1, 2, 4, or 8 CCEs. As to the sizes of these four types of PDCCHs occupying 1, 2, 4, or 8 CCEs, tree aggregation is used, i.e. the PDCCH occupying 1 CCE can start from any CCE location; the PDCCH occupying 2 CCEs starts from even CCE location; the PDCCH occupying 4 CCEs starts from the CCE location which is an integral multiple of 4; and the PDCCH occupying 8 CCEs starts from the CCE location which is an integral multiple of 8.
Each aggregation level defines one search space, including common search space and user equipment-specific (UE-Specific) search space. The number of CCEs of the entire search space is determined by the number of OFDM symbols occupied by the control area indicated by PCFICH in each downlink subframe and the number of PHICH groups. UE carries out blind detection on all the possible PDCCH code rates according to the DCI formats of the transmission modes in the search space.
In the kth subframe, the control domain carrying PDCCH is composed of a group of NCCE,k CCEs numbered from 0 to NCCE,k−1. UE should detect a group of PDCCH candidates in each non-discontinuous reception (non-DRX) subframes so as to acquire control information, and detection refers to decoding the PDCCHs in the group according to all the DCI formats to be detected. The PDCCH candidates to be detected is defined in the manner of search space, and as to aggregation level Lε {1, 2, 4, 8}, the search space Sk(L) is defined by a group of PDCCH candidates. The CCE corresponding to PDCCH candidate m in the search space Sk(L) is defined according to the following formula:L·{(Yk+m)mod └NCCE,k/L┘}+i, 
wherein i=0,L, L−1 m=0,L, M(L)−1, M(L) is the number of PDCCH candidates to be detected in the search space Sk(L).
As to common search space, Yk=0, L takes the values of 4 and 8.
As to UE-specific search space, L takes the values of 1, 2, 4, and 8.Yk=(A·Yk-1)mod D, 
wherein Y−1=nRNTI≠0, A=39827, D=65537, k=└ns/2┘, ns is a slot number in one radio frame. nRNTI is a corresponding RNTI (Radio Network Temporary Identifier).
UE should detect one common search space with the aggregation levels thereof being 4 and 8 respectively and one UE-specific search space with the aggregation levels thereof being 1, 2, 4 and 8 respectively, and the common search space and UE-specific search space may be overlapped. The particular number of detections and the corresponding search space are as shown in Table 1:
TABLE 1Number ofSearch space Sk(L)PDCCHAggregationSizecandidatesTypelevel L[in CCEs]M(L)UE-specific16621264828162Common41648162
UE is semi-statically configured to receive the PDSCH data transmission according to the indication of PDCCH of the UE-specific search space based on one of the following transmission modes by way of a high layer signaling:
Mode 1: Single-antenna port; port 0
Mode 2: Transmit diversity p Mode 3: Open-loop spatial multiplexing
Mode 4: Closed-loop spatial multiplexing
Mode 5: Multi-user MIMO
Mode 6: Closed-loop Rank=1 pre-coding
Mode 7: Single-antenna port; port 5
If the UE is configured by the high layer to perform the PDCCH decoding by using the cyclical redundancy check (CRC) scrambled by cell radio network temporary identifier (C-RNTI), then the UE shall decode the PDCCH and all the relevant PDSCHs according to the corresponding combination defined in Table 2:
TABLE 2UEdownlinkCorresponding PDSCHtransmissionDCItransmission solutionmodeformatSearch spaceof PDCCHMode 1DCIUE specificSingle-antenna port,format 1Adefined by Commonport 0and C-RNTIDCIUE specificSingle-antenna port,format 1defined by C-RNTIport 0Mode 2DCIUE specificTransmit diversityformat 1Adefined by Commonand C-RNTIDCIUE specificTransmit diversityformat 1defined by C-RNTIMode 3DCIUE specificTransmit diversityformat 1Adefined by Commonand C-RNTIDCIUE specificOpen-loop spatialformat 2Adefined by C-RNTImultiplexing ortransmit diversityMode 4DCIUE specificTransmit diversityformat 1Adefined by Commonand C-RNTIDCIUE specificClosed-loop spatialformat 2defined by C-RNTImultiplexingor transmit diversityMode 5DCIUE specificTransmit diversityformat 1Adefined by Commonand C-RNTIDCIUE specificMulti-user MIMOformat 1Ddefined by C-RNTIMode 6DCIUE specificTransmit diversityformat 1Adefined by Commonand C-RNTIDCIUE specificClosed-loop Rank =format 1Bdefined by C-RNTI1 precodingMode 7DCIUE specificIf the number of PBCHformat 1Adefined by Commonantenna ports is 1, and C-RNTIemploy a Single-antennaport, port 0Otherwise, transmitdiversityDCIUE specificSingle-antenna port,format 1defined by C-RNTIport 5Mode 8DCIUE specificIf the number of PBCHformat 1Adefined by Commonantenna ports is 1,and C-RNTIemploy a Single-antennaport, port 0Otherwise, transmitdiversityDCIUE specificdual-layer transmission,format 2Bdefined by C-RNTIport 7 and 8, or Single-antenna port, port 7 or 8
If the UE is configured by the high layer to perform the PDCCH decoding by using the CRC scrambled by the semi-persistently scheduled cell radio network temporary identifier (SPS C-RNTI), then the UE shall decode the PDCCH and all the relevant PDSCHs according to the corresponding combination defined in Table 3:
TABLE 3UEdownlinkCorresponding PDSCHtransmissionDCItransmission solutionmodeformatSearch spaceof PDCCHMode 1DCIUE specificSingle-antenna port,format 1Adefined by Commonport 0and C-RNTIDCIUE specificSingle-antenna port,format 1defined by C-RNTIport 0Mode 2DCIUE specificTransmit diversityformat 1Adefined by Commonand C-RNTIDCIUE specificTransmit diversityformat 1defined by C-RNTIMode 3DCIUE specificTransmit diversityformat 1Adefined by Commonand C-RNTIDCIUE specificTransmit diversityformat 2Adefined by C-RNTIMode 4DCIUE specificTransmit diversityformat 1Adefined by Commonand C-RNTIDCIUE specificTransmit diversityformat 2defined by C-RNTIMode 5DCIUE specificTransmit diversityformat 1Adefined by Commonand C-RNTIMode 6DCIUE specificTransmit diversityformat 1Adefined by Commonand C-RNTIMode 7DCIUE specificSingle-antenna port,format 1Adefined by Commonport 5and C-RNTIDCIUE specificSingle-antenna port,format 1defined by C-RNTIport 5Mode 8DCIUE specificSingle-antenna port,format 1Adefined by Commonport 7and C-RNTIDCIUE specificSingle-antenna port,format 2Bdefined by C-RNTIport 7 or 8
If the UE is configured by the high layer to perform the PDCCH decoding by using the CRC scrambled by transmit power control—PUCCH—cell radio network temporary identifier (TPC-PUCCH-RNTI), then the UE shall decode the PDCCH according to the corresponding combination defined in Table 4:
TABLE 4DCI formatSearch spaceDCI format 3/3ACommon search space
If the UE is configured by the high layer to perform the PDCCH decoding by using the CRC scrambled by transmit power control—PUSCH—cell radio network temporary identifier (TPC-PUSCH-RNTI), then the UE shall decode the PDCCH according to the corresponding combination defined in Table 5:
TABLE 5DCI formatSearch spaceDCI format 3/3ACommon search space
Since the LTE-Advanced network needs to be able to access the LTE users, the operating frequency band thereof needs to cover the current LTE frequency band, and there is already no continuous 100 MHz frequency spectrum bandwidth which can be allocated on this frequency band, one direct technology to be solved by LTE-Advanced is to aggregate several continuous component carriers (frequency spectrum) distributed in different frequency bands by using the carrier aggregation technology to form a 100 MHz bandwidth which can be used by LTE-Advanced. That is, as to the aggregated frequency spectrum, it is divided into n component carriers (frequency spectrums), and the frequency spectrum in each component carrier (frequency spectrum) is continuous.
3GPP provides a PDCCH Monitoring Set (PDCCH Monitoring Set), including downlink component carriers and belongs to a UE DL Component Carrier Set. The user has to monitor the PDCCH on this downlink component carrier. In an LTE-Advanced system, the use of carrier aggregation enables that one downlink component carrier may correspond to a plurality of uplink component carriers, which is different from the situation that only one downlink carrier corresponds to one uplink carrier in the LTE system. And, the method for the blind detection of PDCCH is also different. Moreover, there is still no blind detection method for PDCCH in the related art, which brings inconvenience to the practical application.